Conventional manholes include a lower or bottom pad, a barrel having a relatively constant diameter adjacent the pad, a concentric or eccentric cone extending upwardly from the barrel, one or more adjusting rings to adjust the overall height of the manhole, and a casting frame on top of the adjusting rings to support a lid at an elevation substantially level with the surrounding pavement. The casting frame is preferably sealed to the uppermost adjusting ring to preclude or minimize water flow into the manhole.
One problem with existing manholes is that many were made long ago, and then oftentimes were made of brick. Due to the old age of the manholes, as well as the materials used to make them, many manholes have begun to deteriorate or have damaged areas. The damaged areas create weak spots, which may allow water to infiltrate the sewer system and also lead to the eventual collapse of the manhole.
Methods exist for repairing the walls of manholes. One such method involves the use of a liner and a bladder to repair the manhole wall. The liner and bladder are placed in the manhole, and the bladder is expanded to press the liner against the manhole wall. The liner is impregnated with a resin and pressed against the manhole wall. One problem with this method is that the liner must stretch circumferentially as the bladder expands. Many liners, when stretched circumferentially, will shrink longitudinally to make up for the extra perimeter length needed. Due to the shape of manholes and how bladders expand, liners may affix first approximately midway along the depth of the manhole. Therefore, when the top portion of the liner stretches circumferentially, it does not have the requisite material to take from to account for the larger circumference. Because the liner is anchored at the casting and at the midpoint along the wall of the manhole, this may cause the liner to rip or not fit tightly against the manhole wall to properly repair the wall.
Accordingly, there is a need in the art for an improved method and means that overcomes the problems of a liner ripping or tearing when the liner stretches circumferentially due to the liner becoming affixed to the manhole wall at an undesired first location. Also, this same problem occurs to non-stretching liners, as the length of the liner must be increased as the bladder expands, pressing the liner against the manhole wall.